
Part Name  Description  Manufacturer 
ADC0803MDC  8Bit µP Compatible A/D Converters  National >Texas Instruments 
ADC0803MDC Datasheet PDF : 41 Pages

Functional Description (Continued)
Figure 2 shows a worst case error plot for the ADC0801. All
centervalued inputs are guaranteed to produce the correct
output codes and the adjacent risers are guaranteed to be
no closer to the centervalue points than ±1⁄4 LSB. In other
words, if we apply an analog input equal to the centervalue
±1⁄4 LSB, we guarantee that the A/D will produce the correct
digital code. The maximum range of the position of the code
transition is indicated by the horizontal arrow and it is guar
anteed to be no more than 1⁄2 LSB.
The error curve of Figure 3 shows a worst case error plot for
the ADC0802. Here we guarantee that if we apply an analog
input equal to the LSB analog voltage centervalue the A/D
will produce the correct digital code.
Transfer Function
Next to each transfer function is shown the corresponding
error plot. Many people may be more familiar with error plots
than transfer functions. The analog input voltage to the A/D
is provided by either a linear ramp or by the discrete output
steps of a high resolution DAC. Notice that the error is con
tinuously displayed and includes the quantization uncertainty
of the A/D. For example the error at point 1 of Figure 1 is +1⁄2
LSB because the digital code appeared 1⁄2 LSB in advance
of the centervalue of the tread. The error plots always have
a constant negative slope and the abrupt upside steps are
always 1 LSB in magnitude.
Error Plot
DS00567181
FIGURE 1. Clarifying the Error Specs of an A/D Converter
Accuracy=±0 LSB: A Perfect A/D
Transfer Function
Error Plot
DS00567182
DS00567183
FIGURE 2. Clarifying the Error Specs of an A/D Converter
Accuracy=±1⁄4 LSB
DS00567184
17
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